1. Field of the Invention
The present invention relates to liquid crystal display device, and more particularly, to a shield cover for insulating a transformer and protecting an inverter and a liquid crystal display device using the same.
2. Description of the Related Art
Much effort has been devoted to research and develop various display devices to address the demand of information-driven society. These display devices are divided into luminescent display devices, which emits light spontaneously, and non-luminescent display devices, which do not emit light spontaneously. Examples of luminescent display devices are cathode ray tube (CRT), electro-luminescent display (ELD), light-emitting diode (LED), vacuum fluorescent display (VFD), field emission display (FED), and plasma display panel (PDP).
A liquid crystal device (LCD) is an example of a non-luminescent display device. The LCD device has been most widely used because it is compact, thin, and consumes low power. The LCD device is increasingly being used as a substitute for Cathode Ray Tube (CRT). In addition to being used on mobile devices such as notebook computers, LCD devices have been developed as computer monitors and television displays. The LCD device is being viewed as a next generation display device along with plasma display panel and electro-luminescence display.
Generally, a desired image is displayed on an LCD device by controlling the optical transmittance of a liquid crystal material with data signals that depend on image information. However, the LCD device, which is a non-luminescent display device, does not spontaneously emit light. Each of these data signals corresponds to individual picture elements or pixels arranged in a matrix.
FIG. 1 is an exploded perspective view of an LCD device in accordance with a related art. Referring to FIG. 1, the LCD device includes a liquid crystal display panel 10. A plurality of pixels (not shown) are arranged in the LCD device to form a matrix. Driving circuit units 20 and 30 are provided for driving the pixels. A backlight unit 40 is required for irradiating light on the liquid crystal display panel 10 because the LCD device does not spontaneously emit light. In addition, the LCD device includes various other components for supporting and coupling the liquid crystal display panel 10, the driving circuit units 20 and 30, and the backlight unit 40.
Although not shown, the liquid crystal display panel 10 includes an array substrate and a color filter substrate facing each other. The array substrate and the color filter substrate are attached to each other in such a manner as to maintain a uniform cell gap therebetween. A liquid crystal layer is formed between the array substrate and the color filter substrate.
The driving circuit units 20 and 30 include various devices (not all shown). For example, a timing controller (not shown) is provided for driving the liquid crystal display panel 10. Printed circuit boards (PCB) 21 and 31 are provided, to which tape carrier packages (TCP) 22 and 32 are attached.
A common electrode and a pixel electrode (not shown) are formed within the liquid crystal display panel 10. The common electrode and the pixel electrode generates an electric field through the liquid crystal layer. When a voltage data signal is applied between the pixel electrode and the common electrode, the liquid crystal in the liquid crystal layer is rotated due to the dielectric anisotropy of the liquid crystal in accordance with the electric field generated between the common electrode and the pixel electrode. Accordingly, light is transmitted or blocked at each pixel, thereby displaying a text or an image.
The backlight unit 40 includes a lamp assembly (not shown), a reflection sheet 41, a light guide plate 42, and a plurality of optical sheets 43. The lamp assembly includes a fluorescent lamp (not shown) for emitting light. The reflection sheet 41 reflects light emitted by the fluorescent lamp. The light guide plate 42 guides the emitted light. The optical sheets 43 diffuse and collect light transmitted from the light guide plate 42.
The liquid crystal display panel 10 and the backlight unit 40 are stacked on a mold frame 44. The mold frame 44 supports lateral surfaces of the stacked liquid crystal display panel 10 and the backlight unit 40. An edge of an upper surface of the liquid crystal display panel 10 is pressed against an upper case 51 when the upper case 51 and the mold frame 44 are attached to each other by a screw (not shown).
The liquid crystal display panel 10 and the backlight unit 40 are also supported by a lower case 52. The lower case is arranged at a rear surface of the backlight unit 40. The lower case 52 and the upper case 51 are attached to each other by a screw (not shown).
The LCD device is provided with an inverter for driving a fluorescent lamp. The inverter (not shown) is provided with a plurality of electric components, such as a transformer, an insulating film (not shown), and a shield cover 53. The transformer drives the fluorescent lamp with an alternating current by applying a high voltage to the fluorescent lamp. The insulating film protects the transformer and insulates the transformer from other components by shielding a parasitic magnetic component generated by the transformer. The shield cover 53 protects the inverter from external impact. The shield cover 53 is mounted on the inverter and is attached by a screw (not shown) through the lower case 52 and a screw groove 54, which will be described below.
FIG. 2A is a schematic view of an insulating film attached to an inverter in the LCD device of FIG. 1 in accordance with the related art. Referring to FIG. 2A, the related art LCD device is driven by a direct type backlight. An insulating film 64 made of polyethylene terephthalate (PET) extends from an upper end of a transformer 62 to a lower end of a printed circuit board of an inverter 61. The insulating film 64 protects the transformer 62 within the inverter 61, and insulates the transformer 62 and other components (not shown) by shielding a parasitic magnetic component generated by the transformer 62.
The insulating film 64 is thin, having a thickness of less than 0.1 mm. The insulating film 64 is designed specifically to insulate the inverter 61 and protect the transformer 62. However, the insulating film 64 does not provide protection for the inverter. When the inverter 61 is attached to the LCD device, a shield cover needs be attached to the LCD device, in addition to the insulating film 64, to protect the inverter 61.
FIG. 2B is a schematic view of a shield cover attached to an inverter in the LCD device of FIG. 1 in accordance with the related art. Referring to FIG. 2B, the related art LCD device includes a shield cover 53 made of metal. The shield cover 53 is attached to the lower case 52 to protect the inverter 61, which is mounted at a rear surface of the lower case 52, from external impact. The shield cover 53 is attached to the lower case 52 by a screw through a plurality of coupling grooves 54. A radiating unit 56 is also provided for radiating heat.
In the related art LCD device, the shield cover can electrically interfere with the inverter. Accordingly, a gap is maintained between the shield cover and the inverter. The required height of the gap increases the overall thickness of the LCD device. This increase in overall thickness of the LCD device caused by the shield cover prevents the construction of a slim LCD device according to the related art. Moreover, the shield cover increases a parasitic capacitance between the transformer and a high voltage terminal. Thus, the shield cover degrades the efficiency of the inverter. Accordingly, power consumption of the LCD device is increased, and the uniformity of a displayed white image is degraded.